This invention relates to a light-sensitive silver halide photographic material. More particularly, it pertains to a light-sensitive silver halide photographic material, having a support prepared by electron beam irradiation, which is particularly suitable for photographic printing paper.
As the support for photographic printing paper, for the purpose of rapid photographic processing, use has recently been made of a paper material coated on its surface with a polyolefin resin.
And, for enhancement of the degree of whiteness or the shielding ability of the support, or resolution or sharpness after application of photographic emulsion, an inorganic white pigment such as titanium oxide, calcium carbonate, etc. is incorporated in the polyolefin resin.
Whereas, for formation of a coating of a polyolefin resin, the resin is required to be molten at a high temperature of about 280.degree. to 340.degree. C. And, in a polyolefin resin molten at such a high temperature, it is not possible to incorporate a large amount of an inorganic white pigment and its dispersibility is also poor. For this reason, there is involved the problem that no satisfactory sharpness of the photographic image can be obtained.
In view of the state of the art as mentioned above, a large amount of an inorganic pigment has been attempted to be added in a polyolefin resin by use of a dispersant.
For example, there have been proposed a technique for surface treatment of titanium oxide with a hydrous alumina as disclosed in Japanese Unexamined Patent Publication No. 6531/1976, a technique for surface treatment of titanium oxide with hydrous Al(OH).sub.2 or hydrous Al(OH).sub.2 and hydrous silicon dioxide as disclosed in Japanese Unexamined Patent Publication No. 35625/1977, a technique for coating treatment of titanium oxide with a surfactant as disclosed in Japanese Unexamined Patent Publication No. 108658/1980, a technique for coating treatment of the particle surface of titanium oxide with .beta.-diketone chelate as disclosed in Japanese Unexamined Patent Publication No. 113039/1980, and a technique for coating treatment of particle surfaces of titanium oxide with amines as disclosed in Japanese Unexamined Patent Publication No. 113040/1980.
However, when employing these techniques, during high temperature melting of a polyolefin resin, contamination with the respective additives of an extruder at the die output end may be generated to form concave streaks on the molten film surface, which become the surface groove on the support, whereby coating irregularity of emulsion disadvantageouly occurs.
On the other hand, Japanese Unexamined Patent Publication No. 151942/1982 proposes to use an alkyl titanate in place of the above additives (which function as one kind of dispersants), and above drawbacks are improved.
However, in this case, the pigment treated with an alkyl titanate can be incorporated into the molten polyolefin resin only in an amount of about 10 to 20 wt. %, whereby no sufficient sharpness can be obtained. Also, free alkyl titanate which is not combined with the pigment is liable to be formed, and this may cause fuming during coating through pyrolysis on melting, or may be attached on the cooling roll to form a non-smooth film surface.
Thus, when incorporating a pigment in the polyolefin resin coating of the prior art, no sufficient sharpness can yet be obtained.
Under such a situation, Japanese Unexamined Patent Publications No. 27257/1982 and No. 49946/1982 propose a support for photography having a coated layer prepared by applying coating of a composition curable with electron beam irradiation on a paper substrate and allowing the coating to cure by irradiation of electron beam.
Such a support permits the content of an inorganic pigment to be increased to 20 to 70 wt.%, because coating is carried out at room temperature. Moreover, dispersing can be conducted very easily, with the result that sharpness can be improved by far greater as compared with the polyolefin resin coating.
However, a coating solution containing a resin curable with electron beam and a pigment involves the disadvantage that it is lower in storage stability and cannot be stored for a long time.
Also, after coating, the coating before irradiation of electron beam tends to be agglomerated and give poor filling chracteristic after curing, whereby the surface smoothness of the coated layer will become very bad.
Further, particularly when the amount of the pigment added is increased, the cured layer will become brittle to readily cause generation of stress cracks or stress crazes or lower adhesiveness with paper substrates.
Thus, in the electron beam cured coated layer according to the proposal, no consideration has been paid with respect to affinity or dispersibility between the resin curable with electron beam and the pigment, and also no consideration has been made about the mechanical properties of the coated layer when a large amount of the pigment was added, with the result that no practically satisfactory product can be obtained.
Now, one may consider improvement of dispersibility of the pigment by addition of various kinds of dispersibility enhancers together with the resin curable with electron beam and the pigment.
However, with the use of a conventional dispersibility enhancer such as surfactants, there is neither improved effect of adhesiveness when the amount of the pigment added is increased, nor the effect of embrittlement prevention of the coated layer after curing.
Further, with the use of a conventional dispersibility enhancer, by increase of its amount added, there is also a disadvantage that the coated layer becomes sticky.